1. Technical Field
This disclosure relates to mechanical refiners for pulping wood chips and other comminuted lignocellulosic materials. The application specifically relates to refiner plates used in mechanical refiners.
2. Related Art
Mechanical refiners are employed in the production of pulp material from lignocellulosic material to be used in the making of paper or other paper-based packaging material. Mechanical refiners can also be used to produce pulp from recycled paper material. Mechanical refiners that process recycled material are typically referred to as dispergers or dispersers.
Mechanical refiners may use a flat refining surface, a conical refining surface or a combination of flat and conical refining surfaces. Mechanical refiners may comprise two sets of flat discs, a rotating disc, commonly known as a “rotor,” and a stationary disc, commonly known as a “stator.” Some mechanical refiners may use two rotating discs or the mechanical refiners may use conical-shaped discs configured in either of the previously described manners. Refiner plates are mounted onto discs, which in turn are mounted in the refiner. A gap exists between the discs through which feed material may move. Feed material may comprise wood chips or other cellulosic material. The refining action occurs as feed material passes generally outwardly through the gaps between the opposing relatively rotating discs.
In a mechanical refiner, the feed material is generally acted upon as it moves along the surfaces of the refiner plates thereby allowing for separating and cutting of the material. The refining plate surfaces of the opposing discs in a refiner are typically a combination of bars and grooves facing one-another and crossing each other as at least one of the discs moves, or by a series of intermeshing teeth which cross one-another thereby applying compression and shear forces to the material to be refined. The refiner plates are generally mounted to discs and provide the opposing surfaces for refining. The feed material generally moves through the gap formed between the opposing surfaces of the plates.
Conventional mechanical refiners are generally capable of handling high, medium, or low consistency feed material, whereas conventional dispersers are generally capable of handling recycled feed material. Refiner plates, for a conventional mechanical refiner or a disperser are a critical component of the refining or dispersing equipment and must be capable of handling the feed material (high, medium, or low consistency feed material or recycled or recovered comminuted paper or packaging material used as feed material). The geometries of surfaces of the refiner plates mounted on the discs, such as bars and grooves or intermeshing teeth, typically determine the quality of the work applied to the feed material to be refined.
As feed material moves across the surface of the refiner plates, the surface of the refiner plates tend to wear down and become less effective in providing the desired refining or dispersing action. The wearing of the refiner plates encourages regular changing of the refiner plates to maintain the refining or dispersing performance over time. A typical circle of refiner or disperser plates comprises between 3 and 24 equally-sized segments, which together form a circle.
Mechanical refiners, including dispersers, typically have refiner plates mounted to the discs. These refiner plates are typically made in segments. These segments are generally annularly truncated wedges, such as pie-shaped wedges, but the segments could be other shapes. A series of segments may be mounted adjacent to one another on the disc to form a complete refiner plate.
The “refiner plate segments,” which can describe both mechanical refiner plate segments and disperser refiner plate segments, are usually made of stainless steel or white iron castings machined to fit together as a set in the refiner. The materials used for these segments are relatively hard alloys and the castings require precision machining of all surfaces. This precision machining results in very sharp edges and corners, posing a safety concern to those handling the segments.
Over the years, persons handling the segments have received numerous injuries. While these edges and corners can be buffed by hand to reduce the hazard, hand buffing is time-consuming and costly. There is a long felt need for a less costly, safer machined plate segment.